Buildings, bridges and other civil architecture, over a long period of time, can deteriorate. In other words, structural support members such as beams, pillars, walls, etc. can weaken over time. It is known in the art to use reinforced fabric material to repair weakened support structures. One method of reinforcing deteriorating civil architecture comprises the steps of coating the damaged portion of the structure with a primer, coating a room temperature curable resin over the primer, and adhering a reinforced fabric material over the room temperature curable resin layer. The weakened structure agglutinates with the reinforced fabric material by means of the room temperature curable resin so as to enhance the strength of the weakened structure.
Typically, the reinforced fabric material used in the above described processes is a unidirectional fiber sheet. Generally, such a unidirectional fiber sheet comprises an arranged fiber layer which is prepared from filament tows, a multi axial scrim having a net-like structure which supports the arranged fiber layer, and a release paper which is adhered to the arranged fiber layer and multi axial scrim.
In the above described process, after the unidirectional fiber sheet is applied over the layer of curable resin, the exterior surface of the unidirectional fiber sheet, i.e. the release paper surface, is rolled or patted to insure maximum contact between the unidirectional fiber sheet and the curable resin. Thereafter, the release paper is peeled away from the multi axial scrim. The capacity of this process to strengthen the deteriorating structure is limited by the amount of curable resin which permeates and impregnates the fiber sheet and scrim.
The inventors have observed that the degree to which the curable resin permeates and impregnates the fiber layer is effected by the adhesive coating by which the release paper is secured to the fiber layer and multi axial screen. In particular, the greater the release paper surface area which is covered with adhesive, the less curable resin will permeate and impregnate the arranged fiber layer. Generally, the viscosity of the adhesive is more than several millions centipoise (cps) and the viscosity of the curable resin is almost several ten thousands cps. As a result, the resin can hardly permeate the adhesive layer.
In prior art unidirectional fiber sheets, the entire surface of the release paper which abuts the surface of the fiber layer and multi axial scrim is coated with adhesive. The inventors have observed that when such prior art unidirectional fiber sheets employed, the curable resin does not adequately permeate the fiber layer and scrim. As a result, the agglutinating force between the structure and the unidirectional sheet is deficient and the reinforcing effect of the process less than optimal.